The present invention relates to a gas-insulated switchgear assembly for three-phase alternating current transmission, and more particularly to a layout of components of so-called one-and-a-half CB (circuit breaker) system gas-insulated switchgear assembly.
In a high-voltage substation that has concentrated systems and requires especially high reliability, the so-called one-and-a-half CB (circuit breaker) system is generally adopted as the bus bar system as shown in Japanese Laid Open Patent Hei 11-146522, the entire contend of which is incorporated herein by reference. Three circuit breakers are used in the one-and-a-half CB system for two feeders in order that an accident generated in the bus bar should not affect the system, and moreover the system is taken into consideration not to stop the lines while the circuit breakers, etc. are inspected.
FIG. 9 shows a single line connecting diagram of such a one-and-a-half CB system. That is to say, the first main bus bar 1 and the second main bus bar 2 are respectively fed through the first bushing 28 and the second bushing 29, which are connected to external electric lines. In cases where any breakdown takes place in either the first main bus bar 1 or the second main bus bar 2, the first circuit breaker 3, the second circuit breaker 4 and the third circuit breaker 5 are prepared between the main bus bar 1 and the main bus bar 2 so as to break only the broken part, in order to make the remaining bus bar or the power line operated as being coupled.
In order to keep surely the disconnection, the first to sixth disconnecting switches 6 to 11 are connected to the both ends of the circuit breakers 3 to 5. Namely, the first main bus bar 1 is connected to the first disconnecting switch 6. The first circuit breaker 3, the second disconnecting switch 7, the third disconnecting switch 8, the second circuit beaker 4, the fourth disconnecting switch 9, the fifth disconnecting switch 10, the third circuit beaker 5, the sixth disconnecting switch 11 and the second main bus bar 2 are sequentially connected together in series through the connecting bus bars 12 to 17, following the first disconnecting switch 6.
The connecting bus bar 22 branches off from the connecting bus bar 18 between the second disconnecting switch 7 and the third disconnecting switch 8, and connected to the first feeding line 24 via the seventh disconnecting switch 20. The first feeding line 24 is connected to the first bushing 28 to receive electric power from an external feeding line. Similarly, the connecting bus bar 23 branches off from the connecting bus bar 19 between the fourth disconnecting switch 9 and the fifth disconnecting switch 10, and connected to the second feeding line 25 via the eighth disconnecting switch 21. The second feeding line 25 is connected to the second bushing 29 to receive electric power from an external feeding line.
FIGS. 10 and 11 show an example of the layout of a conventional gas-insulated switchgear assembly comprising such switchgear assemblies constituted of gas-insulated devices. FIG. 10 shows a device for three phases. However, the structure for each phase is the same, so that explanation will be carried out for one phase referring to FIG. 11. Namely, between the first main bus bar 1 and the second main bus bar 2, both being located in parallel with each other, the horizontal type circuit breakers 3, 4 and 5 are connected together in series in the direction substantially perpendicular to the main bus bars. The main bus bars 1 and 2 are located in such a manner that the axis of every phase 1a to 1c and 2a to 2c can be positioned vertically above the first circuit breakers 3 and the third circuit breakers 5. The main bus bars 1 and 2 and the circuit breakers 3, 4 and 5 of every phase are mutually connected via the first and second disconnecting switches 6 and 7, the third and fourth disconnecting switches 8 and 9, and the fifth and sixth disconnecting switches 10 and 11, respectively.
The second disconnecting switches 7 are connected to the third disconnecting switches 8 via the connecting bus bars 18, and the fourth disconnecting switches 9 are connected to the fifth disconnecting switches 10 via the connecting bus bars 19. The upper branch portions (connecting bus bars) 22 and 23 are provided on the connecting bus bars 18 and 19. The horizontal type seventh disconnecting switches 20 and eighth disconnecting switches 21 for lead-out lines are connected to the upper branch portions 22 and 23. All devices mentioned above are accommodated in the building 30.
Furthermore, the connecting bus bars (feeding lines) 24 and 25 are connected to the horizontal outlets of the horizontal seventh and eighth disconnecting switches 20 and 21 for the lead-out lines in the direction perpendicular to the main bus bars 1 and 2. The connecting bus bars 24 and 25 are extended over the main bus bars 1 and 2, and pass through the building 30, then are connected to the bottom portions of the bushings 28 and 29, respectively. Positioning of the bushings 28 (or 29) are determined by the distance M between the bushing charger portion and the connecting portion of the connecting bus bars 24 (or 25) to the bushings.
In the one-and-a-half CB system gas-insulated switchgear assembly mentioned above, there were problems as follows. That is to say, because of difficulty in obtaining a site for a substation and in reducing the dimension of the building 30, it is more and more required that the installing area of the gas-insulated switchgear assembly should be reduced. However, the axes of the circuit breakers 3, 4 and 5 are common, so that the distance A0 between the bushings 28 and the bushings 29 becomes long. As a result, a wide installing area is necessary as a whole.